Hydraulic brake



' June 1,1931.

G. F. M9D'OUGALL HYDRAULiC BRAKE 2' Sheets-Sheet 1 OriginalfFiled July 1. 1933 v INVENTOR. 650E625 fi Ma floz/aau.

June 1, 1937- G. F. MODOUGALL HYDRAULIC BRAKE Original Filed July 1, 1933 2 Sheets-Sheet 2 INVENTOR. C0EG;4' /7C 0000044 A TTORNEYf Patented June 1, 1937 UNITED STATES- HYDRAULIC BRAKE George F. McDougall, Portland,

Hydraulic Brake Company,

reg., assignor to Detroit, Mich., a

corporation of California Original application July 1, 1933, Serial No. 678,627. Divided and this application July 27,

1934, Serial No. 737,170

3 Claims.

This invention relates to'hydraulic brakes for motor vehicles. 1

The present invention is a division of my pending application Ser. No. 678,627, filed July 1, 1933,

Patent No. 2,004,078, and is made in accordance with requirements of the United States Patent Oflice under provision of Rule 42.

.The invention comprehends a fluid compression device for producing pressure upon fluid in a brake system, the compression device being operable through a foot pedallever.

In a preferred embodiment of the invention the fluid compression device is connected in a brake system, and the operation of the device is supplemented by power from the prime mover of the vehicle. The compression device is so constructed and connected in the system that the .operator may feel the brake application as it increases in intensity inmuch the way as an operator appreciates the intensity with which the conventional hydraulic brake is applied when operated solely by the operators own eifort against the resistance encountered.

An object of the invention is to provide a fluid 5 compression device for a brake system including a cylinder and a piston reciprocable in the cylinder to place the fluid in the system under pressure and upon release of the pressure to by-pass the fluid first in one direction and then inanother, so

an that the system may be solidly filled with fluid.

. A feature of the invention is a piston having a headprovided with a plurality of spaced passages controlled by a collapsible leak-proof cup, and a port controlled by a valve carried by a reciprocable member in the skirt of the piston.

Another feature of the invention is apiston having a port, a valve carried by the piston for cooperation with the port, and a thrust member together with means for supporting the thrust member.

The novel features considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawings, in which,-

Fig. 1 is a longitudinal sectional view of a master cylinder assembly in the position of at rest,

that is, in the initial position when the brakes are not applied and where the pump for furnishing auxiliary power is assumed to be in operation;

' by 'a key Ill.

Fig. 2 is a transverse sectional view, substantially on line 2-4, Fig. 1;

Fig. 3 is a transverse sectional view, tially on line 3-3, Fig. 1;

Fig. 4 is a side elevation, partly broken away,

substana well-known brakestructure including a motor cylinder, friction elements operated thereby, and a rotatable drum for cooperation with the friction elements, and

Fig. 5 is a diagrammatical illustration of a pump operable in any convenient manner from the prime mover of a motor vehicle.

Referring to the drawings for more specific details of the invention, 2 indicates a reservoir which under normal conditions stands partly full of liquid. An operating shaft 4, journaled in the side walls of the reservoir, has one end extend-' ing outwardly from the reservoir for the attachment of a foot pedal lever, not shown.

The operating shaft 4 has secured, thereon j within the reservoir a lever 6 secured in position by a bolt 8 and held against relative movement The lever 6 is provided with a lobe l2, the object of which will hereinafter appear, and a rounded end portion l4 serving to transmit the rotary motion of the shaft 4 to a piston l6 movable within a cylinder l8.

The cylinder I8 is suitably mounted on the wall of the reservoir withits open end extending into the reservoir adjacent the bottom thereof. The head of the cylinder has a port 20 connected as by a pipe line or conduit 22 to a brake structure including a motor cylinder 24 having opposed .pistons therein connected respectively to the separable ends of friction elements 26 and 28 arranged for cooperation with arotatable drum 30, and a spring 32 connected between the friction elements serves to return the elements to retracted position and to retain them in this position against suitablestops',

The cylinder l8 has a port 34 adjacent the head of the cylinder. This port communicates with a sleeve 36 in which is threaded anut 38 having a passage 40 controlled by a valve 42 normally held against its seat by a spring 44. The passage 40 communicates with a pipe line or conduit 46 connected to the outlet of a suitable pump 48, the driving shaft 50 of which may be driven from the prime mover of a motor vehicle, and the inlet of the pump is connected. toa pipe line or conduit 52 communicating with'a suitable opening in the bottom of the reservoir 2.

The cylinder it also has a port 54 adjacent the head of the cylinder. This port communicates with a chamber 55 having in one end thereof a valve seat and gasket being held in position by a ring 62 fitting snugly in the chamber and secured against displacement as by a plug 64 threaded in the open end of the chamber. The chamber 56 communicates with a cylinder66 having an open end extending into the-reservoir and provided with a port 68 adjacent the valve seat 58 which also communicates with the reservoir.

The cylinder 66 has therein a. sleeve I0 having a closed end I2 provided with a recess I4 in which is fitted a ball bearing I6 adapted to engage the lobe I2 on the actuating lever 6. The sleeve 70 has therein a reciprocable valve I8 and a spring '80 for urging the valve against the seat 58. The sleeve 10 is also provided with a port 82' communicating with the reservoir to provide free egress and ingress of liquid within the sleeve'to avoid hydraulic resistance and to insure smooth operation of the valve.

The piston I6 is retained in the cylinder I8 by a ring 84 threaded in the openend of thecylinder.

'he piston includes a head 86 and a cylindrical skirt portion 88. The head has an axial port 90 providing a valve seat 92 and a plurality of spaced passages 94, and positioned on the head 86 is a .leak-proof cup 96 held against displacement-by a coil spring 98 interposed between the cup and the head of the cylinder. This spring also serves to return the piston to its normal position upon release of pressure in the cylinder.

A cylindrical section I00 reciprocable in the skirt 88 of the piston has an internal spider I02 providing a plurality of passages I04. The spider supports a stem I06 of a valve I08 adaptable for cooperation with the valve seat 92, and the valve stem has a socket I I0 in which is. seated a ball II2 formed on one end of a rod II4 having on its other end an enlarged portion I I6 provided with a recess H8 for the reception of the rounded end portion I4 of theactuating lever 6.

A coil spring I20 is interposed between the cylindrical section I00 and a stop ring I22 threaded in the skirt of the piston. This spring serves to urge the cylindrical section toward the head of the piston, and since thecylindrical section I00 carries the valve I08, the valve is urged toward its seat 92 to close the port 90. Seated on the stop ring I 22- is a conical spring I24 wound around the rod I I4 and engaging the enlarged portion I I6 of the rod so as to support the rod for engagement with the. rounded end lever 6.

In operation, upon depressing a footpedal lever, not shown, the operating shaft 4 is given a slight rotation to move-the actuating lever 6 through an angle resulting in applying forcethrough the connecting rod. II 4 to move the valve I 08 to its seat 92 to close the port 90 in the headof the cylinder and seal ofithe liquid contained within portion I4 of the actuating the cylinder.

cylinders 24, resulting in. spreading the friction elements 26 and 28' into engagement with the drum 30 to effectively retard rotation. thereof. The intensity with which the friction elements 21 and are engaged with the drum is dependent upon the load on the spring-pressed valve I8. The

initial load on this valve requires substantial pressure to open it, approximately one hundred pounds per square inch in devices of this char:

- draulic brake.

2,082,019 valve seat 58 flanked by a rubber gasket 60', the I acter used on small vehicles, and two hundred pounds or more per square inch on larger vehicles,

it being understood that the motor cylinders 24 generally require about forty to fiity pounds per square inch pressure to overcome the return springs 32 connected between the friction elements 26 and 28.

Upon closing the valve I08 a small additional compression is imposed on the spring 80, and upon further inward movement of the piston IS in the cylinder I8 the spring is compressed to increase the load on the valve I8 so that a greater degree of intensity of brake application follows directly in proportion to the movement of the brake pedal as in the case of the conventional hydraulic brakes.

It is to be observed that, when the pump is in operation, inward movement of the piston I6 in the cylinder I8 resulting in displacement of fluid and reduction of the area in the cylinder I8, the pressure of the fluid delivered by the pump to the cylinder is greatly enhanced, resulting in an increase of speed with which the friction elements of the brake are brought into frictional engage-.

ment with the drum.

It is also to be observed that a large volume of fluidunder pressure obviates-the'n ecessity of the. brake lining It is further to be observed tliart when the is in operation .an extremely ,rapidmovementfof the piston tending'to. applyithe brakes will have much the same efi'e'c't as is'gnowfproduced 'bygthe 1 operation of hydraulic. brakes of .the'conventional type. However, the increase in intensity isinuc'h more rapid than in When pressure developed in the cylinder I8 in excess of the amount requiregl to open the valve 18, the excess pressure acquiredj will' be rethe conventional typefofhylieved by discharge of fluid through the port '54, I

the chamber 5.6, pastthevalve 18, and through the port 68 to the reservoir; hencewith the brake pedal held in .a given position a fixed amount of pressurewill be applied to the brakes regardless of the speed of the prime moverv and of the pump operated thereby.

Further inward movementof the piston results in increasing braking pressure in direct proporthe operator, of course, feeling the increase in pressure due to its eifect on the piston, which is transmitted directly to the operator's foot through valve I 08 and linkage connecting this valve to the operating shaft.

- tion to the amount of movement of the piston,

Upon release of the foot pedal lever, the operating shaft 4 rotates slightly and thereby moves the actuating lever 6 to release the applied force on the rod H4, and hence on the valve I08 'and the-piston I6. With the applied force removed, the piston is returned to its retracted position.

by thespring 98, resulting in release of'pressure in the cylinder I8.

As the piston returns to retracted position, fluidreturns to the cylinder from the motor cylin- -ders' 24. Movement of the fluid from the motor cylinders 24 to the cylinder I8.is due to pressure on the pistons of the motor cylinders 24 imposed by the retractable springs 32 connecting the friction elements 26 and 28.

Due to friction on the column offiuid in .the

- cylinder I8, the conduit 22, and to the'tension of a, spring 98, the piston I6 returns to retracted position slightly in advance or the return of the fluid to the cylinder l8. This causes a partial vacuum in the cylinder l8, resulting in a collapse of the cup 96 and admission of fluid from the f reservoir through the passage 94 to the cylinder.

Further pressure in the cylinder causes the Twp 96 to return to static condition and moves the valve I08 from its seat against the-resistance of the spring I20 to open the port 90 in the head 86 of the piston so that excess fluid may be returned through the port 9ll'to the reservoir 2, it

being understood thatthe spring I20 imposes an initial load of approximately six or eight pounds' to the valve I08.

When the fluid has been completely displaced mm the motor cylinders, the valve Ill-is moved under the influence oi the spring I" to close the port 80 in the head or the piston, the cup -96 having previously returned to static condition,

the apparatus isagain in operative position. It

is, of course, to be understood that the valve I08 is retained in open position when the pump is in operation.

When the prime mover is not in operation, the

f valves 42, "I8 and III will be in closed position.

Under these conditions, upon actuation or the.

brake the piston I6 is reciprocated in the cylinder [8 to displace the fluid in the cylinder through the pipe line 22 to the motor cylinders 24, to effectively spread the friction elements 28 and 2. into engagement with the drum 30.

In this operation the valve 18 does not open because of the initial load imposed thereon by the spring 80 and because of the gradual increase of this load in proportion to the movement of the piston within the cylinder. Upon release oi! applied force on the piston, pressure in the cylinder is released and the piston is returned to its retracted position identically as hereinbefore described. v

Although this invention has been described in connection with certain specific embodiments, the

principles involved are susceptible of numerous other applications'that will readily occur to persons skilled in the art. The invention is, therefore, to be limited-only'as" indicated bythe scope or the appended claims.

Having thus described the'various features oithe invention, whatl claii'n as new and desire to secure by letters' patent' is,-

1. In a. fluid rakesyst'eiii the combination 0! a cylinder, a pistor'i' reciprocable therein, said piaton having a port, a sleeve reciprocable in the piston, a ring in the piston for retaining the sleeveagainst displacement, a spring interposed between the ring and one end of the sleeve, a

spider in the sleeve, a valve on one end of the piston having a port,"a sleeve reciprocahle in the piston, a ring in the-piston for retaining-the sleeve against displacement; a'spider in the sleeve,

a valve on one end of spider for coaction with the port in said piston. a rod universally connected to the other end ot'the spider, a spring surrounding said rod and-interposed between the ring and one end of the sleeve, a head on the rod,

and acentralizing springbetween .the retaining ring and the head.

3. In a fluid brakefsystem fthe combination of a cylinder, 9. piston reciproc'able therein, said pis-" ton having a port, a sleeve reciprocable inthe piston, an interior abutment inthe piston for retaining the sleeve againstxdisplacement, a spi- 'der in the sleeveya valve ongoneend oi. the spider for coaction with the';p"or't it said piston. and pivotally connected tothe other end oi the spider, a spring interposed between said abutment and one end of the sleeve, an' 'mabutment on the rod,

and a centralizing spring between the said abutments on the rod and piston. a

' GEORGE F. MCDOUGALL. 

